Refactor STT

internal/service/static/stt.js

@@ -4,12 +4,12 @@
  * decides what to do with the result.
  *
  * Recording lifecycle: acquire() requests microphone access (async,
- * may prompt) and creates a fresh MediaRecorder; start() begins
- * capturing (synchronous); stop() resolves the audio blob and
- * releases the stream. A fresh stream is acquired per recording and
- * torn down on every stop() so iOS/WebKit never reuses a capture
- * track that TTS playback or an audio-session interruption has
- * quietly killed.
+ * may prompt) and creates the MediaRecorder; start() begins capturing
+ * (synchronous); stop() resolves the audio blob. The stream and
+ * recorder are reused across recordings to avoid codec warmup delay.
+ * Before each acquire(), the track state is checked; if iOS/WebKit
+ * has killed the track due to TTS playback or an audio-session
+ * interruption, a fresh stream is obtained.
  */
 
 /**
@@ -41,19 +41,29 @@ export class STT {
   }
 
   /**
-   * acquire requests microphone access and creates a fresh
-   * MediaRecorder. Always starts clean so iOS never reuses a dead
-   * capture track. Must be called before start.
+   * acquire requests microphone access and creates the MediaRecorder.
+   * If an existing recorder has a live track, it is reused to avoid
+   * codec warmup delay. If the track is dead (e.g., killed by iOS
+   * after TTS playback), a fresh stream and recorder are created.
+   * Must be called before start.
    */
   async acquire() {
+    // Reuse if the existing track is still live.
+    const track = this.mediaRecorder?.stream?.getAudioTracks()[0];
+    if (track?.readyState === 'live') {
+      this.audioChunks = [];
+      return;
+    }
+
+    // Track is dead or doesn't exist — acquire fresh.
     this._release();
 
     const stream = await navigator.mediaDevices.getUserMedia({
       audio: true,
     });
 
-    const [track] = stream.getAudioTracks();
-    if (track?.readyState !== 'live') {
+    const [newTrack] = stream.getAudioTracks();
+    if (newTrack?.readyState !== 'live') {
       for (const t of stream.getTracks()) t.stop();
       throw new Error('microphone unavailable');
     }
@@ -93,6 +103,7 @@ export class STT {
 
   /**
    * stop stops recording, transcribes the audio, and returns the result.
+   * The stream and recorder are kept alive for reuse.
    * @returns {Promise<{text: string, detectedLanguage: string}>}
    */
   async stop() {
@@ -118,10 +129,10 @@ export class STT {
 
   /**
    * _stopRecording stops the MediaRecorder and resolves with the
-   * assembled audio blob, releasing the stream. Returns an empty blob
-   * if there is no active recording, so it is safe to call before
-   * start has run (e.g. if the user released while acquire was still
-   * pending).
+   * assembled audio blob. Does not release the stream or recorder,
+   * so they can be reused. Returns an empty blob if there is no
+   * active recording, so it is safe to call before start has run
+   * (e.g., if the user released while acquire was still pending).
    * @returns {Promise<Blob>}
    * @private
    */
@@ -129,7 +140,6 @@ export class STT {
     return new Promise((resolve, reject) => {
       const mr = this.mediaRecorder;
       if (!mr || mr.state === 'inactive') {
-        this._release();
         resolve(new Blob([]));
         return;
       }
@@ -142,7 +152,7 @@ export class STT {
           if (type?.includes('mp4') || type?.includes('m4a')) {
             this._ext = 'm4a';
           }
-          this._release();
+          this.audioChunks = [];
           resolve(blob);
         },
         { once: true },
@@ -151,7 +161,7 @@ export class STT {
       mr.addEventListener(
         'error',
         (event) => {
-          this._release();
+          this.audioChunks = [];
           reject(event.error);
         },
         { once: true },